The present invention relates to tea processing, or more specifically, a process for manufacturing a black leaf tea that resembles orthodox processed tea but possesses infusion characteristics more akin to CTC processed tea.
Leaf tea may be prepared as green leaf tea or black leaf tea. Generally, to prepare black leaf tea fresh green leaves of the plant Camellia sinensis are withered (subjected to mild drying), comminuted, fermented (in which process enzymes in the tea leaf use atmospheric oxygen to oxidise various substrates to produce brown-coloured products) and then fired (to dry the tea leaves). Green leaf tea is not exposed to the fermentation process. Partial fermentation may be used to produce intermediate-type teas known as xe2x80x9coolongxe2x80x9d tea.
Conventional wisdom dictates that in black tea manufacture tea must be macerated in some way to liberate the fermentative enzymes and their substrates within the leaves. One can macerate tea in many ways but broadly speaking there are two main mechanised methods for doing this.
The first, called xe2x80x9corthodox manufacturexe2x80x9d, involves rolling pre-weighed batches of withered tea leaves prior to fermenting, firing and drying steps. So called xe2x80x9corthodox teaxe2x80x9d is typically characterised by leaf particles that are aesthetically pleasing to many (resemble dried leaves rather than xe2x80x9cgranulesxe2x80x9d of CTC teaxe2x80x94see below) but produce lighter liquors due to less extensive fermentation.
The second method is the most popular of a number of non-orthodox, continuous methods that involves using a machine resembling a mangle that cuts, tears and curls tea leaves. The original machine was invented by W. McKercher in 1930 and is commonly referred to as a CTC (cut-tear-curl) machine. The finely cut product is known generically as xe2x80x9cCTC teaxe2x80x9d and is characterised by a fast infusion rate and strong colour. This method tends to produce tea that is more consistent and uniform in quality and than the orthodox method.
Both orthodox and CTC machines are often used in conjunction with a rotorvane machine, which is a type of extruder used to pre-condition (squeeze/shred) leaves prior to maceration. The rotorvane was invented as a form of continuous orthodox roller, but is rarely used as such today. Liquors generated from rotorvane teas are similar to orthodox in terms of liquor properties and infusion rates. These methods and their history and role in tea manufacture are described in xe2x80x9cTea: Cultivation to Consumptionxe2x80x9d edited by K. C. Willson and M. N. Clifford, Chapman and Hall, 1992.
Generally speaking consumer preference for either orthodox or CTC tea is a matter of national or regional culture. In many countries the visual appearance and texture of leaf tea are important indicators of quality, larger leaf particles being associated with higher quality. In Western markets tea is increasingly purchased in filter paper bags and the colour of the infused product tends to be more important.
Some consumers however want the best of both worlds; i.e. a leaf tea that looks and feels like orthodox processed tea but has the liquor characteristics of a fuller fermented CTC processed tea. Unfortunately there is no commercially available tea manufacturing equipment that can deliver such a leaf tea.
In response to those needs, the applicant has developed methods for manufacturing black leaf teas that resemble orthodox processed tea but infuse like CTC processed tea.
Our international patent application WO 99/40799 discloses one method for manufacturing fast infusing whole or large leaf teas that involves subjecting whole tea leaves to a heat shock at a temperature and for a duration that is sufficient to initiate fermentation, and enabling the tea to ferment for a time and at a temperature that is sufficient to achieve desired liquor properties.
Our international patent application WO 00/10401 discloses another method for manufacturing fast infusing whole or large leaf teas. In that method whole leaf tea is impregnated tea leaves with liquid carbon dioxide within a pressure vessel, depressurising the vessel at a rate that is sufficient to freeze the liquid carbon dioxide, applying sufficient heat to cause the frozen carbon dioxide to sublime and consequently initiate fermentation within the leaves, allowing the tea to ferment for a time that is sufficient to achieve desired liquor properties, and drying the fermented product to yield the whole leaf tea.
The present inventors have developed a third method for manufacturing black leaf teas that resemble orthodox processed tea but infuse like CTC processed tea. This method provides at least a useful alternative to those methods, and has the advantage of potentially utilising existing tea manufacturing equipment (but in a novel fashion; although novel equipment can also be utilised to roll and/or mix the two dhool streams).
In broad terms the present invention relates to a process for manufacturing black tea comprising the steps of: withering a first supply of freshly plucked tea leaves, macerating the withered leaves, allowing the macerated withered leaves to ferment to produce macerated dhool; withering a second supply of freshly plucked tea leaves; mixing the macerated dhool obtained from said first supply of leaves with the withered leaves obtained from said second supply of leaves, rolling the mixture, allowing the rolled mixture to ferment; and drying the fermented mixture to yield black leaf tea.
Black leaf tea made in this way resembles orthodox processed leaf tea but infuses in freshly boiled water at a rate in excess of that of the equivalent mass of the same size grade tea that has undergone orthodox processing. Indeed the tea preferably infuses at a rate that is comparable to that of the equivalent mass of the same tea that has undergone CTC processing.
The first supply of freshly plucked tea leaves is preferably macerated using a CTC machine. It is especially preferable to pass the leaves through a rotorvane machine and then a CTC machine.
The macerated dhool preferably comprises between 10 and 50% of the mixture on a dry weight basis, especially between 15 and 40%, more especially about 35%.
There is a custom (particularly practised in South India) of adding tea dust back in to the tea manufacturing process (usually the CTC process). Such teas are termed xe2x80x9creconditionedxe2x80x9d, and the objective is to xe2x80x9cupgradexe2x80x9d poor quality dust through its incorporation in to new grades. These teas are judged to be poor quality by tea tasters. The present inventors have shown that even when high quality dust is used in the process of the present invention (in place of dhool) a lower quality (less coloured liquor) product results compared to when dhool is used.
The mixture of the macerated dhool obtained from said first supply of leaves and the withered leaves obtained from said second supply of leaves is preferably rolled using a rotorvane machine.
xe2x80x9cTeaxe2x80x9d for the purposes of the present invention means leaf material from Camellia sinensis or Camellia assamica. It also includes rooibos tea obtained from Aspalathus linearis however that is a poor source of endogenous fermenting enzymes. xe2x80x9cTeaxe2x80x9d is also intended to include the product of blending two or more of any of these teas.
xe2x80x9cLeaf teaxe2x80x9d means tea that contains one or more tea origins in an uninfused form.
xe2x80x9cBlack leaf teaxe2x80x9d means substantially fermented leaf tea.
For the avoidance of doubt the word xe2x80x98comprisesxe2x80x99 is intended to mean including but not necessarily xe2x80x9cconsisting ofxe2x80x9d or xe2x80x9ccomposed ofxe2x80x9d. In other words the listed steps or options need not be exhaustive.